1. Field of the Invention
The present invention relates to a power generation complex plant having a control switch, such as a power generation complex plant equipped with a desalination plant having high stability and control response.
2. Description of the Related Art
Recently, a power generation complex plant equipped with a desalination plant which uses exhaust steam of a power generation facility to generate product water has been utilized in, for example, an area suffering from a water shortage.
Such a power generation complex plant is utilized when at least one of electricity and water is necessary. Specifically, there has been proposed a power generation complex plant capable of improving the power generation efficiency in a part-load operation and reducing the total annual fuel consumption (e.g., refer to Jpn. Pat. Appln. KOKAI Publication No. 2006-266258).
A power generation complex plant generally has a configuration shown in FIG. 12. This power generation complex plant 100P comprises a steam consuming facility 110P, a steam generating facility 120P, a high-pressure steam header 130P, a steam turbine power generation facility 140P, a low-pressure steam header 150P, a steam bypass facility 160P, a steam generating facility control unit 170P, a regulator valve control unit 180P and a steam bypass facility control unit 200P.
The steam consuming facility 110P uses steam such as exhaust steam of the power generation facility. For example, a desalination facility, which uses steam to generate product water, corresponds to the steam consuming facility 110P. Together with the steam consuming facility 110P, a condensing facility 111P for condensing extra steam may be installed.
The steam generating facility 120P generates steam for use in the steam turbine power generation facility 140P and the steam consuming facility 110P. The steam generating facility 120P is, for example, an exhaust heat recovery boiler for using an exhaust gas of a gas turbine as a heat source to generate steam. In particular, an exhaust heat recovery boiler with an auxiliary combustor in which a duct burner is added to an ordinary exhaust heat recovery boiler, for example, corresponds to the steam generating facility 120P.
The steam generated by the steam generating facility 120P is supplied into the high-pressure steam header 130P.
The steam turbine power generation facility 140P generates electricity by use of the steam supplied from the high-pressure steam header 130P. The steam turbine power generation facility 140P has a regulator valve 141P for adjusting the volume of inflow steam.
The steam flowing in from the steam turbine power generation facility 140P is supplied into the low-pressure steam header 150P. The steam consuming facility 110P is configured to use the steam supplied from the low-pressure steam header 150P. In addition, when the volume of steam desired by the steam consuming facility 110P is small, extra steam in the low-pressure steam header 150P is supplied to the condensing facility 111P and cooled down into condensed water.
The steam bypass facility 160P links the high-pressure steam header 130P to the low-pressure steam header 150P in such a manner as to bypass the steam turbine power generation facility 140P. The steam bypass facility 160P adjusts the volume, pressure, and temperature of the steam supplied from the high-pressure steam header 130P and then supplies the steam to the low-pressure steam header 150P. The steam bypass facility 160P has a bypass valve 161P and a bypass spray valve 162P for adjusting the volume of passing steam. In addition, this steam bypass facility 160P is used, for example, in the case where the steam consuming facility 110P is operated without operating the steam turbine power generation facility 140P.
The steam generating facility control unit 170P controls the steam generating facility 120P on the basis of the steam pressure in the high-pressure steam header 130P.
The regulator valve control unit 180P has a low-pressure controller 181P, a high-pressure controller 182P, a switch determining unit 183P and a control switch 184P. The regulator valve control unit 180P opens and closes the regulator valve 141P of the steam turbine power generation facility 140P to control the volume of steam to be supplied to the steam turbine power generation facility 140P.
The low-pressure controller 181P controls the steam supplied from the high-pressure steam header 130P to the steam turbine power generation facility 140P, that is, the position of the regulator valve 141P of the steam turbine power generation facility 140P, on the basis of the steam pressure in the low-pressure steam header 150P. The high-pressure controller 182P controls the steam supplied from the high-pressure steam header 130P to the steam turbine power generation facility 140P on the basis of the steam pressure in the high-pressure steam header 130P. The steam supplied to the steam turbine power generation facility 140P, that is, the position of the regulator valve 141P of the steam turbine power generation facility 140P, is controlled by selecting either the low-pressure controller 181P or the high-pressure controller 182P. However, this is normally controlled by the low-pressure controller 181P.
The switch determining unit 183P determines, from the steam pressure in the high-pressure steam header 130P, that the volume of steam desired by the steam consuming facility 110P is beyond the maximum volume of steam to be generated by the steam generating facility 120P. That is, the switch determining unit 183P determines that the volume of steam desired by the steam consuming facility 110P is beyond the maximum volume of steam to be generated by the steam generating facility 120P when the steam pressure in the high-pressure steam header 130P is lower than a preset threshold value.
The control switch 184P makes a switch from the low-pressure controller 181P to the high-pressure controller 182P to control the position of the regulator valve 141P of the steam turbine power generation facility 140P, when the switch determining unit 183P determines that the steam pressure in the high-pressure steam header 130P is lower than the threshold value.
The steam bypass facility control unit 200P opens and closes the bypass valve 161P and the bypass spray valve 162P to control the volume of steam passing through the steam bypass facility 160P. Here, a temperature decreasing facility 163P is provided for the steam bypass facility control unit 200P. Then, the bypass spray valve 162P opens such that sprayed water is supplied to the temperature decreasing facility 163P. Consequently, the temperature of steam is controlled.
Here, for the power generation complex plant 100P having such a configuration, the low-pressure steam header is generally controlled by the low-pressure controller 181P of the steam turbine. The reason for this is that control by a high-pressure controller 182P leads to a higher volume of steam flowing into the steam turbine power generation facility 140P and the steam bypass facility 160P, and thus to unstable control of the whole power generation complex plant. On the other hand, it is not appropriate to perform control solely by the low-pressure controller 181P without the high-pressure controller 182P. The reason for this is that the steam pressure in the high-pressure steam header 130P may drop faster when the volume of steam desired by the steam consuming facility 110P has increased, which may prevent from maintaining the efficiency of the whole power generation complex plant.
Accordingly, the power generation complex plant 100P comprises the control switch 184P to suitably switch between the control by the low-pressure controller 181P and the control by the high-pressure controller 182P.
However, the steam turbine power generation facility 140P and the steam bypass facility 160P may operate more than necessary due to the switch between the control by the low-pressure controller and the control by the high-pressure controller, resulting in deteriorated stability and control response. The control logic may become more complicated by additional switching control.